There has been a proposal of a suction type floating head device which imparts operating steps that a slider of the floating head is pushed on a rotary magnetic disc and a floating force is imparted such that crushing of the head is caused, with damage to both the head and surface to balance them, when the revolution of the rotary magnetic disc reaches to a predetermined revolution speed.
However, in the conventional suction type floating head device, the stability of the head slider is not easily maintained to cause a head crush and to cause a damage of both of the head and the rotary magnetic disc because various forces are applied to the head slider.
Referring to FIGS. 1 and 2, one embodiment of the conventional floating head device will be illustrated.
FIG. 1 is a schematic view of the embodiment and FIG. 2 is a sectional view and a pressure distribution diagram for illustrating a principle of the operation.
In FIG. 1, a head slider (1) is made of magnetic substance and the head slider (1) and a plurality of head parts with a plurality of gaps (3) are formed in one piece. The head slider (1) has a floating surface (4) for imparting a floating force in the operation, an inlet end taper (5) and a suction surface (6) for imparting a sucking force in the operation. The head slider (1) is held on a head holder (10) through a pressure spring (9) and is pushed on a recording surface (8) of a recording disc (7) by the pressure spring (9).
When the recording disc (7) is rotated relative to the head slider (1) in the arrow line direction at a relative speed U, a floating force F1 is imparted at the floating surface (4) of the head slider (1) so as to depart the head slider (1) from the recording surface (8) by air flow from the inlet end A through the outlet end B.
On the other hand, the suction surface (6) tapers away from the recording surface (8) in the direction from A to C; so that air flow caused by relative revolution between the recording disc (7) and head slider (1) creates a hydrodynamic negative pressure that is, a sucking force F2 is imparted so as to cause the head slider (1) to approach the recording surface (8). Thus, during the operation, the floating force F1 the sucking force F2 and pushing force F3 of the pressure spring (9) are applied to the head slider (1) whereby a small floating distance is maintained between the floating surface (4) and the recording surface (8) and an elevation angle .theta.1 between the floating surface (4) and the recording surface (8) and an elevation angle .theta.2 between the suction surfaces (6) and the recording surface (8) are maintained and three forces are automatically balanced.
In the graph of the pressure distribution corresponding to the sectional view of FIG. 2, the sucking force F2 has pressure distribution shown by a curve L to the air flow direction A-C on the suction surface (6). The center of the sucking force F2 is at a position D for a distance m from the air inlet end A to A-C. The distance m is usually given by the equation; EQU m=(0.2 to 0.4).times.(distance between A and B)
The moment produced at the center of the point O by the sucking force F2 is in a clockwise direction. In order to balance to the moment of the sucking force F2, the floating force F1 should be at the point E in the side of the air inlet end A from the point O of the head slider (1). Thus, the floating force F1, the sucking force F2 and the pushing force F3 of the pressure spring (9) are balanced at the side A of the air inlet end of the head slider (1). However, the three forces are respectively balanced at positions spaced from the point O, whereby various moments are formed and the stability of the head slider (1) is not easily maintained to cause the head crush sometimes.